The present invention relates to an image forming device, such as a facsimile device, and more particularly to an image forming device having a driving force transmission mechanism for transmitting a driving force of a drive motor to a sheet feeding mechanism.
In a driving device for a facsimile device in the related art, to meet requirements, such as a reduction in device size and a reduction in cost, a driving force of a single drive motor is switch-transmitted by means of a driving force transmission mechanism to a plurality of driving members, such as feed rollers for feeding recording sheets, and feed rollers for feeding documents. For example, in a facsimile device equipped with a driving device as disclosed in U.S. patent application Publication Ser. No. 2002/0118395, the destination to which the driving force is to be transmitted by the driving force transmission mechanism is switched according to the operation mode, such as the image reading mode or the recording mode, so as to transmit the driving force of the drive motor solely to the selected feed rollers required to be driven for the selected operation mode.
FIG. 1 is a schematic diagram showing an example of the driving force transmission mechanism in a facsimile device of a related art.
This driving force transmission mechanism includes a sun gear 43, a rotary member 45, two planetary gears 46, 47, a motor gear 82, four transmission gears 61, 62, 63, 64 and a sensor switch 80. The sun gear 43 includes a large diameter gear 43A and a small diameter gear 43B coaxially and integrally with the large diameter gear 43A. The rotary member 45 is provided coaxial with the sun gear 43, and is selectively connected to the sun gear 43 through a one-way clutch (not shown). The rotary member 45 is formed into a disc-like shape and has an outer peripheral portion provided with five recesses 60 and five projections 60′ arrayed alternately in a circumferential direction with circumferential lengths different from each other. The two planetary gears 46 and 47 are provided at predetermined positions on the surface of the rotary member 45 facing the sun gear 43 so as to be in meshing engagement with the small diameter gear 43B of the sun gear 43. The motor gear 82 is fastened to the rotor of a drive motor (not shown) and is in meshing engagement with the large diameter gear 43A of the sun gear 43. The four transmission gears 61, 62, 63, and 64 are provided at predetermined positions about the sun gear 43. Each transmission gear is meshedly engageable with the planetary gears 46 and 47 when the planetary gears 46 and 47 are orbitally moved about the sun gear 43. The sensor switch 80 is provided at an appropriate position about the sun gear 43 and adapted to detect the recesses 60 and projections 60′ formed in the outer periphery of the rotary member 45 as the rotary member 45 rotates.
The five projections 60′ of the rotary member 45 is includes one elongated projections 60a′ and four shortened projections 60b′. Similarly, the five recesses 60 of the rotary member 45 includes one elongated recess 60a and four shortened recesses 60b. Assuming that a position of the elongated projection 60a′ is a reference position, the elongated recess 60a is situated at a position spaced apart from the reference position by approximately 225 degrees as measured counterclockwise therefrom in FIG. 1.
When the sun gear 43 rotates counterclockwise, the rotary member 45 is connected to the sun gear 43 by the one-way clutch, and rotates with the sun gear 43. When the sun gear 43 rotates clockwise, connection with the sun gear 43 is canceled, so that the rotary member 45 does not rotate. Further, a rotation regulating member 51 is provided for preventing the rotary member 45 from rotating in a clockwise direction (reverse rotational direction) when the rotary member 45 is set at a predetermined position corresponding to the operation mode, such as the image reading mode or the recording mode.
The transmission gear 61 is adapted for transmitting the driving force of the drive motor (not shown) to a feed roller (not shown) by way of the sun gear 43 for feeding recording sheets. The transmission gear 62 is adapted for transmitting the driving force to a spool (not shown) for taking up the ink ribbon and to a platen (not shown) for feeding the recording sheets at the printing position. The transmission gear 63 is adapted for transmitting the driving force to a feeding roller (not shown) for discharging recording sheets that have undergone printing. The transmission gear 64 is adapted for transmitting the driving force to a document feeding roller (not shown) for feeding documents, and to a line feed roller (not shown) and to a document discharge roller (not shown).
Driven gears 75, 74, and 73 are respectively fixed to the shafts of the document feeding roller, the line feed roller, and the document discharge roller. A driven gear 72 is provided between the driven gear 74 and the driven gear 73 and is meshedly engaged therewith to make the rotating directions of the driven gear 74 in coincidence with that of the driven gear 73. Further, the driven gear 72 is connected to the transmission gear 64 through a driven gear 71 for speed reduction.
In the facsimile device of related art, in order to transmit the driving force of the drive motor to the proper roller to be driven for performing the desired operation mode such as the image reading mode and the recording mode, the rotary member 45 is rotated counterclockwise to a position where the planetary gears 46 and 47 are engaged with the desired one of the transmission gears 61,62, 63, 64 those connected to these rollers. The rotating position of the rotary member 45 is detected upon detection to the recesses 60 of the rotary member 45 by the sensor switch 80.
FIG. 1 shows a state in which the facsimile device has been set to the image reading mode. In this state, the driving force transmission mechanism is adjusted such that the rotary member 45 is at a position where the planetary gear 46 is in meshing engagement with the transmission gear 64 connected to the document feeding roller for feeding documents, the line feed roller, and the document discharge roller. The setting of the rotary member 45 to the position corresponding to the image reading mode is effected by rotating the sun gear 43 counterclockwise, causing the sensor switch 80 to detect the shortened recess 60b provided on the left side of the elongated projection 60a′, whereupon the planetary gear 46 is brought into meshing engagement with the transmission gear 64, and the rotation regulating member 51 prevents the rotary member 45 from rotating in the clockwise direction.
When the rotary member 45 is set to the position corresponding to the image reading mode, the planetary gear 46 is in mesh with the transmission gear 64 as shown in FIG. 1, so that the driving force of the drive motor can be transmitted to the transmission gear 64 by way of the sun gear 43 and the planetary gear 46. Further, the driving force of the drive motor can be transmitted to the driven gears 75, 74, and 73 fixed to the shafts of the document feeding roller, the line feed roller, and the document discharge roller by way of the driven gears 71 and 72.
When transmitting the driving force of the drive motor to the driven gears 75, 74, and 73, the sun gear 43 is rotated clockwise as indicated by the arrow in FIG. 1. As is apparent from driving connection among the planetary gear 46, the transmission gear 64, and the driven gears 71 through 75 as shown in FIG. 1, when the sun gear 43 is rotated clockwise, the driven gear 75 for driving the document feeding roller rotates clockwise, whereas the driven gear 74 for driving the line feed roller and the driven gear 73 for driving the document discharge roller rotate counterclockwise. The rotating direction of the driven gear 75 and that of the driven gears 74 and 73 are opposite to each other because the document feeding roller feeds a document to the line feed roller side (to the right in FIG. 1) while in pressure contact with the obverse surface of the document, whereas the line feed roller and the document discharge roller feed the document to a discharge opening (not shown) side (to the right in FIG. 1) while in pressure contact with the reverse surface of the document.
Thus, in the image reading mode, the rotary member 45 is set to the state as shown in FIG. 1, and the drive motor is rotated counterclockwise. Accordingly, the driving force is transmitted to the driven gears 73 through 75 by way of the sun gear 43, the planetary gear 46, the transmission gear 64, and the driven gears 71 and 72, and as a result, the driven gears 73 and 74 and the driven gear 75 rotate counterclockwise and clockwise, respectively, to thereby feed the document.
In the above-described driving device, in which the driving force of a single drive motor is switch-transmitted to a selected one of the plurality of feeding rollers for providing a selected one of the operation modes by way of the driving force transmission mechanism, the following problem may occur. When sheet jamming or the like occurs during feeding of a document or a recording sheet and the feeding operation is stopped, the user attempts to pull out the document or the recording sheet toward the upstream side with respect to the feeding direction in order to remove the sheet or the document. However, the document or the recording sheet will be constrained by the feeding roller, making it impossible to deal with the jamming, and in some cases, the document or the recording sheet may suffer damage and remain in the feeding path.
For example, in the image reading mode, during feeding of a document the document feeding operation is stopped due to document jamming or the like, and the user pulls the document toward the upstream side with respect to the feeding direction in an attempt to remove the document. This pulling action imparts document feed roller to rotate counterclockwise, and at the same time, imparts the line feed roller and the document discharge roller to rotate clockwise. Thus, a counterclockwise torque is applied to the driven gear 75, and a clockwise torque is applied to the driven gears 73 and 74. That is, the driven gears 73 through 75, to which the planetary gear 46 is drivingly connected through the intermediation of the driven gears 71 and 72 and the transmission gear 64, receive a force causing the driven gears 73 through 75 to rotate in a direction opposite to the document feeding direction.
When the force is applied to the driven gears 73 through 75 for rotating the driven gears 73 through 75 in a direction opposite to the document feeding direction, a counterclockwise torque is applied to the transmission gear 64, with the result that a clockwise torque is applied to the planetary gear 46, and that a counterclockwise torque is applied to the sun gear 43. However, since the rotation of the sun gear 43 is restricted by the motor gear of the drive motor, rotations of the planetary gear 46, the transmission gear 64, and the driven gears 71 through 75 drivingly connected to the sun gear 43 are also restricted.
As a result, none of the document feeding roller, the line feed roller, and the document discharge roller those nipping the document, can rotate. Accordingly, if the user pulls the document toward the upstream side, a frictional force between the feeding rollers such as the document feeding roller and the document increases to cause the document to be constrained by the feeding rollers, making it impossible to deal with the jamming. In some cases, this may damage the document.
Incidentally, when the user performs the operation of pulling the document toward the downstream side in FIG. 1, a clockwise torque is applied to the transmission gear 64, and a counterclockwise torque is applied to the planetary gear 46. Thus, when the gears 64 and 46 rotate clockwise and counterclockwise, respectively, the planetary gear 46 moves slightly counterclockwise to cancel the engagement between the two gears, and the transmission gear 64 becomes free. Therefore, upon the document pulling action in the downstream side, all of the document feeding roller, the line feeding roller, and the document discharge roller can rotate, thus involving no such problem incurred when pulling the document toward the upstream side.
The above-described problem also occurs in case of feeding a recording sheet.